Zinc Porphyrins with a Pyridine‐Ring‐Anchoring Group for Dye‐Sensitized Solar Cells

Anchoring groups are extremely important in controlling the performance of dye‐sensitized solar cells (DSCs). The design and characterization of sensitizers with new anchoring groups, in particular non‐carboxylic acid groups, has become a recent focus of DSC research. Herein, new donor? π? acceptor zinc? porphyrin dyes with a pyridine ring as an anchoring group have been designed and synthesized for applications in DSCs. Photophysical and electrochemical investigations demonstrated that the pyridine ring worked effectively as an anchoring group for the porphyrin sensitizers. DSCs that were based on these new porphyrins showed an overall power‐conversion efficiency of about 4.0 % under full sunlight (AM 1.5G, 100 mW cm^?2).     

Interaction between tetramethylcucurbit[6]uril with α-furaldehyde-isonicotinyl-hydrazone hydrochloride

Interaction between tetramethylcucurbit[6]uril (TMeQ[6], host) and the hydrochloride salt of α-furaldehyde-isonicotinyl-hydrazone hydrochloride (FIHH⁺, guest) was investigated using X-ray crystallography and spectroscopic methods. X-ray crystallography showed that the π–π stacking effect and hydrogen bonding resulted in the formation of a dumbbell-shaped supramolecule which contained two FIHH⁺@TMeQ[6] host–guest inclusion complexes. The host–guest interaction provided identifiable changes in the vibrational frequencies in the IR spectra. ¹H NMR spectral analysis established a similar interaction model and revealed that TMeQ[6] preferred to include the furan moiety over the pyridine moiety of the FIHH⁺ guest molecule. Absorption spectrophotometric analysis suggested that the host and guest interact in a ratio of 1:1 with a stability constant K _s = (3.52 ± 0.74) × 10⁶ l mol^? 1.pH titration confirmed that the host–guest interaction led to a clear change in the protonation constant of the title guest. Quantum chemical calculations were used to determine the possible mechanism of formation of the dumbbell-shaped complex.     

Synthesis and Properties of Poly(Aryl Ether Ketone) Copolymers with Trifluoromethyl‐Substituted Benzene in the Side Chain

The new monomer (4‐(4′‐trifluoromethyl)phenoxyphenyl)hydroquinone (TFPOPH) was synthesized in a three‐step synthesis. A series of poly(aryl ether ketone) copolymers were prepared by the reaction of (4‐(4′‐Trifluoromethyl)phenoxyphenyl)hydroquinone and hydroquinone (HQ) with 4,4′‐difluorobenzophenone (DFB) in the presence of potassium carbonate in tretramethylene sulfone (TMS). Thermal analyses of the fluorinated copolymers showed that the glass transition temperature and 5.0% weight loss temperature are similar with that of PEEK, and the crystallinity decreased with increasing of TFPOPH. For the copolymer synthesized with the molar fraction of TFPOPH in the diphenol monomers (TFPOPH, HQ) being over 0.2, no cold crystallization temperature and melting temperature were detected, indicating that these copolymers are almost amorphous. The crystal structure of the copolymers with the molar fraction of TFPOPH being not higher than 0.2 is rhombic. The solubility in polar aprotic solvents of poly(aryl ether ketone)s copolymers increases and dielectric constant decreases step by step.     

Stereoselective Synthesis of Phosphorus Analogs of (R)-Carnitine and (R)-Gabob

Bioreduction of 3-substituted-2-oxoalkanephosphonates by baker's yeast afforded corresponding 2-hydroxy-alkanephosphonates in good yields and ee value. These compounds ( 2a,b ) could serve as useful chirons for the stereoselective synthesis of phosphorus analogs of (R)-Carnitine and (R)-GABOB.     

Rapid Synthesis of N-Acyl Ureas from Their Thio Analogues Using Wet Silica-Supported Permanganate Under Solvent-Free Conditions

A rapid method to N-acyl ureas from corresponding N-acyl thioureas is described. N-coumaroyl-N′-arylthioureas, which are easily prepared by the reaction of coumarin-3-carboxylic acid chloride with potassium thiocyanate and arylamines, can be expeditiously transformed into corresponding N-acyl ureas via r.t. grinding with wet silica supported potassium permanganate under solvent-free conditions in an excellent yield.     

Flammability and Thermal Oxidative Degradation Kinetics of Magnesium Hydroxide and Expandable Graphite Flame Retarded Polypropylene Composites

The flammability and the thermal oxidative degradation kinetics of expandable graphite (EG) with magnesium hydroxide (MH) in flame‐retardant polypropylene (PP) composites were studied by limiting oxygen index (LOI), UL‐94 test, and thermogravimetric analysis (TGA). The results show that EG is a good synergist for improving the flame retardancy of PP/MH composite and the effect is enhanced with decreasing EG particle size. The Kissinger method and Flynn‐Wall‐Ozawa method were used to determine the apparent activation energy (E) for degradation of PP and flame retarded PP composites. The data obtained from the TGA curve indicate that EG markedly increases the thermal degradation temperature of PP/MH composites and improves the thermal stability of the composites. The kinetic results show that the values of E for degradation of flame retarded PP composites is much higher than that of neat PP, especially PP/MH composites with suitable amount of EG, which indicates that the flame retardants used in this work have a great effect on the mechanisms of pyrolysis and combustion of PP.     

Preparation and Characterization of Linear and Miktoarm Star Side-Chain Liquid Crystalline block Copolymers with p-Methoxyazobenzene Moieties via a Combination of ATRP and ROP

One linear and two miktoarm star side-chain liquid crystalline (LC) block copolymers with p-methoxyazobenzene moieties were prepared by a combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) techniques. First, ROPs of ε -caprolactone (ε -CL) were carried out catalyzed by Sn(Oct)₂ using three multifunctional initiators, hydroxyethyl 2-bromoisobutyrate (AB type), 3-hydroxy-2-(hydroxymethyl)-2-methylpropyl 2-bromo-2-methylpropanoate (A₂B type) and 2,2-bis(hydroxymethyl)propane-1,3-diyl bis(2-bromo-2-methylpropanoate) (A₂B₂ type), at 110°C in toluene, respectively. Second, the previously obtained poly(ε -caprolactone)s (PCLs) with bromines functionalities were used as the macroinitiators to conduct ATRP of 6-(4-methoxy-4-oxy-azobenzene) hexyl methacrylate (MMAZO) with CuBr/PMDETA as the catalyst systems at 85°C in anisole to prepare the linear and miktoarm side-chain LC block copolymers (PCL-b-PMMAZO, (PCL)₂-(PMMAZO) and (PCL)₂-(PMMAZO)₂). The produced polymers were well-controlled with the controlled molecular weights and the relatively narrow molecular weight distributions (M _w/M _n ≤ 1.35). The structures of the obtained polymers were all characterized by NMR, FT-IR and GPC analysis. Furthermore, the LC properties of the linear and miktoarm star block copolymers were also investigated by differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM).     

Synthesis and Properties of pH-Responsive Polymers with Cadaverine Side Groups

A water-soluble monomer N¹-(4-vinylbenzyl)-pentane-1,5-diamine dihydrochloride (VBPDA) with cadaverine (1,5-pentanediamine) group was synthesized. pH-responsive polymer with cadaverine group was obtained by free radical polymerization of VBPDA using 4,4-azobis(4-cyanovaleric acid) (ACVA) as the initiator. The structure and molecular weight of the polymer were characterized by FTIR, ¹H-NMR and GPC-MALLS. Aggregation behavior of the polymer in aqueous solution was investigated by dynamic light scattering (DLS), UV-Vis and fluorescence measurements. The experimental results show that the fluorescence intensity of the aggregates decreases and the size of the aggregates increases with increasing pH due to the continuous dehydration of the cadaverine side groups.     

Inclusion Interactions of Cucurbit[7]uril with Adenine and its Derivatives

Interactions of cucurbit[7]uril (Q[7] host) with guest adenine (g1), adenosine (g2) and 2′,3′-o-isopropylideneadenosine (g3) were studied in details by ¹H NMR, UV absorption spectroscopy, fluorescence spectroscopy and high performance liquid chromatography (HPLC) methods. We found that the suitable pH range for interaction was between 1 and 7, and the optimal pH range was between 2 and 4. The ¹H NMR analysis indicated that Q[7] selectively interacted with the adenine moiety of the guests g1 and g2, while Q[7] selectively interacted with the D-ribose sugar ring moiety of the guest g3. Moreover, ¹H NMR spectra showed that the exchange between the bound guest and the free guest was fast on the NMR time scale for the Q[7]-g1 and Q[7]-g2 systems. However, an obvious equilibrium between the bound host/guest and the unbound host/guest were observed in the Q[7]-g3 complex. Several methods were used to determine quantitatively the stability of the three host–guest inclusion complexes formed between Q[7] and the guests. The formation constants by UV and fluorescence were 1.90 × 10⁵ L mol^? 1 and 1.34 × 10⁵ L mol^? 1 for Q[7]-g1, 9.41 × 10⁴ L mol^? 1 and 4.24 × 10⁴ L mol^? 1 for Q[7]-g2, 4.50 × 10⁴ L mol^? 1 and 3.62 × 10⁴ L mol^? 1 for Q[7]-g3, respectively. HPLC method was also introduced to explore the interactions between Q[7] and the adenine and its derivatives. The formation constants of the host–guest inclusion complexes, as determined by HPLC, were 6.76 × 10⁴ L mol^? 1 for Q[7]-g1, 1.80 × 10⁴ L mol^? 1 for Q[7]-g2, 3.01 × 10⁴ L mol^? 1 for Q[7]-g3 respectively. Our study suggested that Q[7] could be a suitable host for the delivery of bioactive molecules, such as the adenine and its derivatives.